Effects of Native and Non-native Fishes on Native Apple Snail Population Dynamics

Science Center Objects

The Florida apple snail is a critical component of the state's wetland food webs. USGS scientists assess the effects of native and non-native fishes on the native snail populations.

Researchers collecting data on apple snails

Researchers collecting data on apple snails

(Public domain.)

The Science Issue and Relevance: The Florida apple snail (Pomacea paludosa) is a critical component of central and south Florida wetland food webs. Most notably, it is the main food source of the endangered snail kite (Rostrhamus sociabilis). Any changes to the apple snail population have the potential to impact the region’s snail kite populations. Everglades apple snail populations have suffered declines in the last 10 - 20 years, and fish could exert predation pressure on apple snails and further reduce their populations.  However, it is unknown whether native and non-native fishes differentially affect apple snails.  Efforts to understand and consequently mitigate non-native fish impacts is important for the Everglades’ restoration plans and management efforts.

Mesocosm tanks used for the apple snail experiments.

Mesocosm tanks used for the apple snail experiments.

(Public domain.)

Methodology for Addressing the Issue: To quantify the effects of native and non-native fish predators on apple snail populations we are comparing the impacts of one known native fish predator, redear sunfish (Lepomis microlophus), with two non-native fishes, African jewelfish (Hemichromis letourneuxi) and Mayan cichlid (Cichlasoma urophthalmus). We are focusing on fish effects on snail growth, reproduction, physical damage, and mortality. This study directly addresses the question of how predation affects snail population dynamics and could be contributing to the slow recovery of Everglades snail populations that suffered population declines.

Future Steps: EverSnail is a landscape-scale model of Everglades apple snail populations developed by USGS (with the University of West Florida) and used by USFWS and US Army Corps of Engineers to analyze alternative management scenario impacts on snail kites. The proposed project will provide data to inform EverSnail.